1. Упростите выражение: 15√20 − 4√45 + 2√125 − 7√80 − √2.

\(\sqrt{20}=2\sqrt{5}\), \(\sqrt{45}=3\sqrt{5}\), \(\sqrt{125}=5\sqrt{5}\), \(\sqrt{80}=4\sqrt{5}\).

\(15\cdot2\sqrt{5}-4\cdot3\sqrt{5}+2\cdot5\sqrt{5}-7\cdot4\sqrt{5}-\sqrt{2}=\)

\(=30\sqrt{5}-12\sqrt{5}+10\sqrt{5}-28\sqrt{5}-\sqrt{2}=-\sqrt{2}\).

Ответ: \(-\sqrt{2}\)